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Has anyone done this?

I had to make my own barrel nut for neck attachments, because I can't find them at all in Taiwan.

I took a 10mm medium carbon steel rod, drilled and tapped it for M6, then I used a propane torch to heat treat it (heat until glowing then dunk in water, and reheat until it turns yellow and let cool) so it doesn't strip on me. It works well so far.

However I heard of the tenon cracking when using a barrel nut, so what can you do to prevent it?

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

See my post in the linked thread for graphics and photo. We use a graphite epoxy (aka carbon fiber) strip set into the end of the tenon as shown in the thread...1/16" x 3/8" or so. A wood reinforcement would work as well to reinforce the tenon to prevent a bearing-type failure where the barrel but pulls through the tenon.

viewtopic.php?f=10101&t=51190&p=674183&hilit=tenon+reinforcement+failure#p674183

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For the times they are a changin'

- Bob Dylan

I’m just wondering if sinking a wood screw alongside the tenon would reinforce it?

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

I believe that would actually work against the nature of the joint. A cross-grain reinforcement as discussed in the referenced thread discourages failure of the tenon where the barrel nut bears by converting what is a shear load into a bending load on the reinforcement, and - once distributed across the tenon - as a pure tensile load.

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For the times they are a changin'

- Bob Dylan

Just a thought for you:

If you have to make barrel nuts from scratch, and then perform modifications on the tenon to make up for the design flaws associated with using a round nut instead of a square nut, then why not avoid some work and just make a better nut in the first place?

We use barrel nuts because they are readily available, and making something that works better takes more work. You don’t have them readily available. So don’t use them.

Trevor Gore cuts a square mortise into the heel of the guitar, then puts a square rod into the mortise. The square rod is drilled and tapped before installation. There are holes in the end of the tenon that match up with the threaded holes in the square rod. He swears by the results. The square stock doesn’t cause the same problems that round barrel nuts cause.

You are a metal worker, so this should be easy for you.

I just don’t see the point of you making barrel nuts from scratch when you can make something better.

You can buy cross dowel barrel nuts on eBay. If you like making them that's fine too.

I think you're misunderstanding what I'm proposing.

I mean to say to pre-drill a hole at the bottom of the tenon across the grain up the tenon. A very long wood screw is then epoxied into it and the head ground off, so that the barrel nut bears against the steel rod rather than cross grain.

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

I believe that would act to distribute the shear load, and the screw would carry some reasonable bending load, but would also create its own set of bearing stresses on what is a very shallow section of tenon.

Replacing the screw with a smooth rod and gluing it in place would be stronger, although there is not that much long-grain glue area left after a 1/8" diameter max rod is glued in place (leaving about 1/32" on each side of the rod). Flattening the rod for more glue area might help, but will take up more of the space between the body end of the barrel nut opening and end of tenon, leaving less wood to carry the shear loads caused by the bending of the flattened rod.

This is likely the primary reason why wood or graphite cross-grain strips are commonly set into the tenon end for pull-through reinforcement - adequate bending stiffness, adequate strength, and lower weight than metal reinforcement. Another option might be a laminated loose tenon glued into a milled recess in the neck.

The other complicating factor is a perfectly drilled hole in what is a 3/16" to 7/32" thick x 3" to 3-1/2" deep area...and perfectly parallel and square to the face of the tenon. Likely not an issue with a good milling machine and quality drill bit, followed with a .125" chucked reamer, but much more of a challenge than making a slot or rabbet with a tablesaw or band saw.

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For the times they are a changin'

- Bob Dylan

I do not ice Robbie O Brien doesn't really mention any shortcomings, so in practical terms, how easy is it to actually break such a joint? Would a light bump cause it to fail?

Right now it's just too late to do any reinforcements like this because that would mean I'd have to take the fingerboard off.

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

I have another idea...

What about machining a tenon or even just an insert out of aluminum, machine aggressive texture into the aluminum to aid in glue adhesion, coat the aluminum in Alodine (a chemical treatment that makes aluminum take to glues or coatings aggressively), then just route a slot into the end of a neck and glue it in?

The threaded aluminum would hold the screw well, and it would have enough tensile and shear strength to handle any abuse a guitar should handle.

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

When it gets to that stage, I'd be practicing dovetails....or building myself a neck jig thingy.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Why? Are dovetails far more reliable?

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

Search "dovetails joints" for opinions.
I use the Gore method mentioned above by Don, aluminium could also be used.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

This is my opinion on dovetails. They're ok, and can be fitted. However what detracts from it is 1. It requires a huge amount of work/repair in order to undo a dovetail. 2. If the dovetail is not fitted with exact precision/tolerances, it will fail. 3. If the glue used were to fail for whatever reason, it will fail, and 4. I find no matter how closely fitted the joint is, wood will compress over time under strain (and acoustic guitar neck joint is under about 200lb of force), coupled with the guitar being stored in a not so ideal environment (like the jungles of Malaysia, Vietnam, etc.) the glue can and sometimes comes apart, necessitating expensive repair work.

So mortise/tenon, bolt on, etc. works better because it's a mechanically fastened joint, meaning under normal circumstances will never come apart, especially if a belleville washer is used. I used O Brien's barrel nut method because they're easy for me to make, and I don't know if I trust inserts to not come apart at some time (never happened but you know). I thought using aluminum inserts would negate any wood grain failure of the mortise and tenon joint.

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

I won’t try to convince you that you should use a dovetail; you can make up your own mind about that. One quibble that I have with your reasons for not wanting to use a dovetail: If you fit it correctly, the glue is almost entirely superfluous. It is a mechanical joint. The glue is just extra insurance against failure, not an essential part of the joint. Note that I’m talking about the glue inside the dovetail, not the glue under the fingerboard extension. That glue is important, dovetail or bolt-on.

Regarding your aluminum tenon idea, I think the point Colin was making with his dovetail comment is that your tenon idea seems to be an awful lot of work and overengineering. And you don’t even know if it will work. Around here, we call that going around Robin Hood’s barn to get somewhere. In other words, it is a circuitous path.

I still think that, if you have to make something like neck attachment nuts from scratch, why not make something that you know will work better than barrel nuts? The Trevor Gore square rod idea works. It would be easy for a metal worker such as yourself. And getting it to work inside a neck is way easier than your aluminum tenon idea (no offense), which is untested.

Just my opinion.

I like that! - "going around Robin Hood’s barn to get somewhere"

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

If you use it in conversation, Colin, make sure to drop the “to get somewhere” part. I added that here to clarify the meaning. If someone were to propose a very complicated route to the store, you would say “that’s going around Robin Hood’s barn.”

You know that we here in Appalachia are mostly the descendants of Scottish and Irish immigrants, right? I figure an awful lot of our colorful language came with our ancestors and just developed a bit over time. Whatever we are here, it started over there!

When I made my dovetail joint, I made a rather snug fit but even then, if I were to pull on it (unglued) very hard the heel still slides out. So it doesn't look like it will work without glue.

Should I make it so tight that it's impossible to install it without heavy clamping force? That's the only way I can see glue not being needed to hold the joint. Because the wood still compresses a bit when you pull on the neck... even if the joint fits perfectly.

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

Well, think about how you were able to get the dovetail loose. Dovetails only loosen in one direction: the neck coming vertically out of the pocket. If it is truly a snug fit between the neck and the body, then when you glue the fingerboard to both the neck and the body, the neck really cannot move in that vertical fashion unless and until you unglue the fingerboard extension from the body. Moreover, at tension, the strings are not pulling the neck straight up out of the pocket; they are mostly pulling the neck toward the butt of the guitar, with a "hinge" at the neck/body joint. If anything, that force keeps the dovetail snug, assuming it was snug to begin with.

So what I am saying is that, when the whole joint goes together (including the fingerboard), the glue inside the dovetail joint is not doing much.

No heavy clamping force should be used. In fact, the glue will immediately start to swell the wood so you actually want light clamping force to close the dovetail before you add glue.

I think what I'm saying is, when I did a dovetail if I were to bend a neck upward (does that make sense?) with medium force, the heel wants to pull away from the body and the fingerboard has not moved from the top, just like how string tension want to bend the neck upward.

I would of course correct its geometry so the fit is better but even with perfect fit if I pull hard (not nearly as hard as the string would pull on it, but still hard) the wood compresses and the heel pulls away from the body.

So you're saying the glue should swell the wood and keep this from happening. But then a few years down the road the heel pulls away from the body, possibly because the owner kept it in a slightly damp environment. It just seems it depends so much on a highly precise degree of hand fitting and if there were to be a 1 angstrom gap somewhere, it will fail.

At least bolt on neck with every failure mode addressed would never have this happen, even if the guitar isn't kept in strictly ideal environments to where no possibility the glue would soften even slightly. As long as the bolt is properly torqued, it's never going to come loose. Even better if you used loctite to make sure that would never happen.

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

If you get a gap at the heel when you put string-like pressure on the neck, then your dovetail was not fitted properly. No offense intended; it's just not how the joint is supposed to respond to that force. If that is how your neck responded to that force, then the joint was not fitted properly.



I don't think that is what Barry was saying at all. I think he was recommending that you account for swelling when it comes time to actually glue the joint together. Swelling might prevent you from getting the snug fit you thought you had. If Barry meant something different, I figure he will correct us both. But to me, the point is that glue swelling is a thing you should factor into any gluing operation where you want a snug fit. The bad thing that might happen is that you have a snug fit when dry, but then the glue swells the wood before you get the pieces together, then they won't fit together anymore. So, make the parts snug when dry, but not super snug. Swelling is a problem to be managed and accounted for, not a solution to a problem.

Like I said, I really don't want to be in a position where I am trying to convince you to use a dovetail. Use whatever you want to use.

That's exactly what I meant. I remember the story about DeAquisto's first guitar where he made the sliding dovetail snug, added the glue and then was only able to seat the neck about 2/3 deep. I think his dovetail was more of a parallel shape than the normal V shape.

My point is that I don't want to over use clamping pressure to close the neck joint. It should close dry with moderate hand pressure.

I saw a Martin neck, unfinished, that was dovetail but has an insert in it.

It almost looks like Martin has a bolt even in their dovetail neck, probably to reduce warranty claims.

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

That insert is for finishing purposes not used in the dovetail joint. Actually tightening a bolt in that directions would only serve to try to pull the bearing surfaces of the dovetail away from the cheeks. This would essentially make it a bolt on mortise and tennon joint since the load would be put on the bearing surface of the heel and body rather than the bearing surface of the dovetail and pocket.

The dovetail neck joint tightens as it slides down so you couldn't really line up a bolt hole with the insert reliably anyway (assuming any work was done to properly fit the dovetail).

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.